U.S. patent number 6,770,101 [Application Number 09/973,562] was granted by the patent office on 2004-08-03 for prostatic stent and delivery system.
This patent grant is currently assigned to SciMed Life Systems, Inc.. Invention is credited to Joseph P. Desmond, III, James A. Teague.
United States Patent |
6,770,101 |
Desmond, III , et
al. |
August 3, 2004 |
Prostatic stent and delivery system
Abstract
A collapsible and expandable stent includes a body segment,
first and second terminal ends spaced apart from each other, a
substantially smooth wall and a lumen extending between the first
and second ends. The device can be used for maintaining the patency
of the prostatic urethra in a male patient. The stent may be
designed according to the individual needs of particular patients.
A delivery system for deploying the stent and other collapsible and
expandable stents in the body of the patient comprises a
retractable sheath, a shaft and a locking element to reversibly
lock the sheath to the shaft.
Inventors: |
Desmond, III; Joseph P.
(Bloomington, IN), Teague; James A. (Spencer, IN) |
Assignee: |
SciMed Life Systems, Inc.
(Maple Grove, MN)
|
Family
ID: |
25521028 |
Appl.
No.: |
09/973,562 |
Filed: |
October 9, 2001 |
Current U.S.
Class: |
623/23.66;
623/23.64 |
Current CPC
Class: |
A61F
2/94 (20130101); A61F 2/95 (20130101); A61F
2/04 (20130101); A61F 2250/0039 (20130101); A61F
2002/047 (20130101); A61F 2220/005 (20130101); A61F
2220/0058 (20130101); A61F 2230/0078 (20130101) |
Current International
Class: |
A61F
2/06 (20060101); A61F 2/00 (20060101); A61F
2/04 (20060101); A61F 002/36 () |
Field of
Search: |
;604/8,104
;623/1.18,1.2,1.3,1.31,1.34,1.46,23.64,23.66,23.7 ;600/29,30
;606/108,153,191,194,195 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
197 13 280 |
|
Oct 1998 |
|
DE |
|
1 110 561 |
|
Jun 2001 |
|
EP |
|
2 767 673 |
|
Mar 1999 |
|
FR |
|
1 412 774 |
|
Jul 1988 |
|
SU |
|
WO 00/44308 |
|
Aug 2000 |
|
WO |
|
Other References
Copy of International Search Report for International Patent
Application No. PCT/US02/31723, mailed from the International
Search Authority on Jan. 13, 2004. .
Stoeckel et al., "Superelastic Ni-Ti Wire", Wire Journal
International, pp. 45-50, Mar. 1991. .
Teague et al., 09/829,705, "Reinforced Retention Structures", Filed
Apr. 10, 2001..
|
Primary Examiner: McDermott; Corrine
Assistant Examiner: Matthews; William H
Attorney, Agent or Firm: Testa, Hurwitz & Thibeault,
LLP
Claims
What is claimed is:
1. A stent comprising, first and second terminal ends spaced apart
from each other, at least one of the first and second terminal ends
comprising a retention ring having an expanded ring state and a
collapsed ring state, and a wall, disposed between the first and
second terminal ends, and including an inner surface and an outer
surface, the inner surface defining a lumen extending between the
first and second terminal ends, and the outer surface having a
substantially smooth portion, the wall having, a first outside
cross-sectional diameter at the first terminal end, a second
outside cross-sectional diameter at the second terminal end, at
least one intermediate outside cross-sectional diameter at an
intermediate location between the first and second terminal ends,
each of the first and second outside cross-sectional diameters is
greater than the intermediate outside cross sectional diameter and
the outer surface of the wall tapers down from each of the first
and second terminal ends to the at least one intermediate location,
and an expanded state and a collapsed state, the wall being adapted
to spontaneously revert from the collapsed state to the expanded
state, wherein the retention ring is adapted to spontaneously
revert from the collapsed ring state to the expanded ring state
and, in the expanded ring state, the retention ring extends axially
from the wall of the stent.
2. A stent according to claim 1 wherein the first terminal end of
the stent is adapted for residing at a bladder end of a prostatic
urethra of a patient and the second terminal end of the stent is
adapted for residing at an external sphincter end of the prostatic
urethra.
3. A stent according to claim 1 wherein the substantially smooth
portion of the outer surface of the wall is adapted to inhibit
tissue-in-growth.
4. A stent according to claim 1 wherein the retention ring includes
an annular elastic core.
5. A stent according to claim 4 wherein the annular elastic core
includes a nickel-titanium alloy.
6. A stent according to claim 1 wherein the first terminal end
includes a retention ring, having an expanded ring state and a
collapsed ring state, and being adapted to spontaneously revert
from the collapsed ring state to the expanded ring state to
facilitate retention of the retention ring within the bladder of
the patient, and in the expanded ring state, the retention ring
extending axially from the wall of the stent.
7. A stent according to claim 1 wherein the second terminal
includes a retention ring, having an expanded ring state and a
collapsed ring state, and being adapted to spontaneously revert
from the collapsed ring state to the expanded ring state to inhibit
the retention ring from passing through an external sphincter of
the prostatic urethra of the patient, and in the expanded ring
state, the retention ring extending axially from the wall of the
stent.
8. A stent according to claim 1 wherein the first terminal end
includes a first retention ring having a first expanded ring state
and a first collapsed ring state and being adapted to spontaneously
revert from the first collapsed ring state to the first expanded
ring state to facilitate retention of the first retention ring
within the bladder of the patient, the first retention ring
extending axially from the wall of the stent in the first expanded
ring state, and wherein the second terminal end includes a second
retention ring having a second expanded second ring state and a
second collapsed ring state and being adapted to spontaneously
revert from the second collapsed ring state to the second expanded
ring state to inhibit the second retention ring from passing
through the external sphincter of the prostatic urethra of the
patient, the second retention ring extending axially from the wall
of the stent in the second expanded ring state.
9. A stent according to claim 1 wherein the wall further comprises
at least one through aperture extending between the inner surface
and the outer surface for providing fluid communication between the
inner surface and the outer surface.
10. A stent according to claim 1 wherein the first outside
cross-sectional diameter is greater than the second outside
cross-sectional diameter.
11. A stent according to claim 1 wherein the second outside
cross-sectional diameter is greater than the first outside
cross-sectional diameter.
12. A stent according to claim 1, wherein the first terminal end
comprises a domed segment having inner and outer surfaces and
extending axially from the wall of the stent and adapted for
facilitating insertion of the stent into the patient.
13. A stent according to claim 12 wherein the domed segment further
comprises at least one through aperture extending radially between
the inner and outer surfaces of the domed segment to provide fluid
communication between the inner and outer surfaces of the domed
segment.
14. A stent according to claim 13 wherein the domed segment further
comprises an axially extending protuberance adapted for
facilitating insertion of the stent into a patient.
15. A stent according to claim 14 wherein the axially extending
protuberance has a through aperture sized to accommodate a guide
wire.
16. A stent according to claim 1 wherein the wall of the stent
includes a radio-opaque material.
17. A stent according to claim 1 wherein the wall comprises a
coating.
18. A stent comprising, first and second terminal ends spaced apart
from each other, at least one of the first and second terminal ends
comprising a retention ring having an expanded ring state and a
collapsed ring state, and a wall, disposed between the first and
second terminal ends, and including an inner surface and an outer
surface, the inner surface defining a lumen extending between the
first and second terminal ends, and the outer surface having a
substantially smooth portion, the wall having, a first outside
cross-sectional diameter at the first terminal end, a second
outside cross-sectional diameter at the second terminal end, at
least one intermediate outside cross-sectional diameter at an
intermediate location between the first and second terminal ends,
wherein each of the first and second outside cross-sectional
diameters is greater than the intermediate outside cross sectional
diameter and the outer surface of the wall tapers down from each of
the first and second terminal ends to the at least one intermediate
location; and wherein, in the expanded ring state, the retention
ring extends axially from the wall of the stent, and an expanded
state and a collapsed state, the wall being adapted to
spontaneously revert from the collapsed state to the expanded
state.
19. A stent according to claim 18 wherein the first terminal end of
the stent is adapted for residing at a bladder end of a prostatic
urethra of a patient and the second terminal end of the stent is
adapted for residing at an external sphincter end of the prostatic
urethra.
20. A stent according to claim 18 wherein the substantially smooth
portion of the outer surface of the wall is adapted to inhibit
tissue-in-growth.
21. A stent according to claim 18 wherein the retention ring is
adapted to spontaneously revert from the collapsed ring state to
the expanded ring state.
22. A stent according to claim 21 wherein the retention ring
includes an annular elastic core.
23. A stent according to claim 22 wherein the annular elastic core
includes a nickel-titanium alloy.
24. A stent according to claim 18 wherein the first terminal end
includes the retention ring adapted to spontaneously revert from
the collapsed ring state to the expanded ring state to facilitate
retention of the retention ring within the bladder of the
patient.
25. A stent according to claim 18 wherein the second terminal
includes the retention ring adapted to spontaneously revert from
the collapsed ring state to the expanded ring state to inhibit the
retention ring from passing through an external sphincter of the
prostatic urethra of the patient.
26. A stent according to claim 18 wherein the wall further
comprises at least one through aperture extending between the inner
surface and the outer surface for providing fluid communication
between the inner surface and the outer surface.
27. A stent according to claim 18 wherein the first outside
cross-sectional diameter is greater than the second outside
cross-sectional diameter.
28. A stent according to claim 18 wherein the second outside
cross-sectional diameter is greater than the first outside
cross-sectional diameter.
29. A stent according to claim 18 wherein the wall of the stent
includes a radio-opaque material.
30. A stent according to claim 18 wherein the wall comprises a
coating.
31. A stent comprising, a first terminal end including a first
retention ring, the first retention ring having a first expanded
ring state and a first collapsed ring state and being adapted to
spontaneously revert from the first collapsed ring state to the
first expanded ring state to facilitate retention of the first
retention ring within the bladder of a patient; a second terminal
end spaced apart from the first terminal end and including a second
retention ring, the second retention ring having a second expanded
second ring state and a second collapsed ring state and being
adapted to spontaneously revert from the second collapsed ring
state to the second expanded ring state to inhibit the second
retention ring from passing through the external sphincter of the
prostatic urethra of the patient; and a wall, disposed between the
first and second terminal ends, and including an inner surface and
an outer surface, the inner surface defining a lumen extending
between the first and second terminal ends, and the outer surface
having a substantially smooth portion, the wall having, a first
outside cross-sectional diameter at the first terminal end; a
second outside cross-sectional diameter at the second terminal end,
at least one intermediate outside cross-sectional diameter at an
intermediate location between the first and second terminal ends,
wherein each of the first and second outside cross-sectional
diameters is greater than the intermediate outside cross sectional
diameter and the outer surface of the wall tapers down from each of
the first and second terminal ends to the at least one intermediate
location, and an expanded state and a collapsed state, the wall
being adapted to spontaneously revert from the collapsed state to
the expanded state, wherein, in the first expanded ring state, the
first retention ring extends axially from the wall of the stent
and, in the second expanded ring state, the second retention ring
extends axially from the wall of the stent.
Description
TECHNICAL FIELD
This invention relates to stents used to maintain a body lumen,
such as the prostatic urethra, and to systems for delivering stents
into these body lumens.
BACKGROUND INFORMATION
Stents are a known class of medical device for expanding or
maintaining an open lumen or passageway in various body cavities,
vessels, or ducts. Stents have been employed, for example, in the
urethra, the ureters, the biliary tract, the cervix, the rectum,
the esophagus and blood vessels to relieve the pathological effects
of constrictions occurring in these passageways.
Bladder obstruction arising from enlargement of the prostate gland
in males is one of the most commonly encountered disorders in
urology. The prostate gland lies under the bladder and surrounds
the passageway known as the prostatic urethra, which transfers
fluids from the bladder to the sphincter and ultimately outside the
body. An enlarged prostate gland constricts the prostatic urethra
leading to a condition known as benign prostatic hyperplasia
("BPH"). BPH causes a variety of obstructive symptoms, including
urinary hesitancy, straining to void, decreased size and force of
the urinary stream, and in extreme cases, complete urinary
retention possibly leading to renal failure. A number of other
irritating symptoms may also accompany BPH, including urinary
frequency and urgency, nocturnal incontinence, and extreme
discomfort.
Known stents used to combat BPH may not ensure patient safety and
comfort. Indeed, existing stents, such as wire mesh stents, may
become entangled with prostate tissue leading to infection and
discomfort. Under such conditions, prostate tissue often penetrates
the perforations of the wire mesh stent rendering it difficult, if
not impossible, to remove without surgical intervention. Other
devices, such as Foley catheters are retained in the bladder by a
balloon inflated with sterile water or saline. This necessitates
use of a collection bag to catch fluids drained from the bladder,
thereby reducing a patient's quality of life. In addition, many
stents cannot accommodate unusually or abnormally shaped prostatic
urethras or prostatic urethras of varying lengths and widths.
Also, internal forces from involuntary bodily functions (such as
peristalsis and other secretory forces, as well as patient
movement) may force some stents out of their intended position
within the prostatic urethra. For instance, the bladder can exert
intense pressure during urination, which tends to expel a stent
positioned within the prostatic urethra. It is also possible that
normal body motions, such as walking or running may displace a
stent at this location.
SUMMARY OF THE INVENTION
In one embodiment, the invention reduces the risk of
infection/inflammation, while also maintaining patient comfort and
preventing migration of the stent out of the prostatic urethra.
According to one feature, the outer surfaces of the stent are
smooth, and do not become entangled with and/or potentially infect
internal body tissue. Structural features of certain embodiments of
the invention, including a double funnel or hourglass
configuration, ensure that the stent will not dislodge or migrate
out of its intended position. According to another feature the
stent is easy to insert, and should circumstances warrant, easily
removed without the need for invasive surgery. In addition, the
stent may be designed according to the individual needs of
particular patients by tailoring its dimensions to accommodate
prostatic urethras of various sizes and shapes.
One aspect of the invention relates to a collapsible and expandable
stent including first and second terminal ends spaced apart from
each other, a substantially smooth wall disposed between the first
and second terminal ends and a lumen extending between the first
and second terminal ends. Preferably, the stent is designed for use
in the prostatic urethra of a male patient, and is constructed of
flexible biocompatible materials such as elastomeric compounds.
Materials like these combine rigidity with the softness necessary
for patient stability and comfort. To help retain the stent in
place in a body of a patient, at least one of the first and second
terminal ends is wider than at least some portion of the wall
disposed between the terminal ends.
To further help anchor the stent in the body, the first and second
terminal ends may further include a retention ring having an
elastic member. Where both the first and second terminal ends
include retention rings, these retention rings are preferably
aligned in a substantially parallel relationship. By varying the
size of the retention rings, the stent can accommodate prostatic
urethras of different sizes and shapes. The retention rings may be
constructed from the same elastomeric compounds used in the first
and second terminal ends. According to one aspect, the rings
incorporate an elastic member to provide rigidity to the device and
to ensure that the device reverts spontaneously to its
predetermined configuration from its collapsed state.
In one embodiment, both the first and second terminal ends are
wider than at least some portion of the wall. Under this
construction, the wall extending between the terminal ends forms a
double funnel or hourglass configuration. Once placed in a patient,
this double funnel configuration acts to maintain the stent in
position within an open passageway. When placed in the prostatic
urethra, for example, one of the first or second terminal ends
rests at the bladder end of the prostatic urethra and allows for
drainage of urine into the prostatic urethra. The other of the
first or second terminal ends sits above the external sphincter to
prevent migration into the bulbous urethra while maintaining
drainage through the prostate.
A lumen may extend between the first and second terminal ends to
allow drainage of fluids through the passageway. Alternatively or
additionally, drainage may be provided or enhanced by grooves
located on the wall. In addition, the wall may define one or more
through-holes disposed along its length to provide for fluid
communication with the lumen to further facilitate drainage.
In another embodiment, one of the first and second terminal ends
further comprises a dome structure. The dome may define at least
one aperture, and terminates in a protuberance. The wall of this
embodiment may include at least one annular collar to provide
breaking points for the device entering its collapsed state. To
further enhance collapsibility, the wall may define one or more
slots. The slots may comprise openings through, or concave surfaces
along the wall.
According to one embodiment, the stent of the invention includes a
coating material. The coating material may be disposed continuously
or discontinuously on the surface of the stent. Further, the
coating may be disposed on the interior and/or the exterior
surface(s) of the stent.
The coating material may include, but is not limited to a medicinal
composition that leaches into the wall of a body lumen after
implantation (e.g. to deliver a therapeutic agent to the body
lumen). The coating is preferably a polymeric material, which is
generally provided by applying to the stent a solution or
dispersion of preformed polymer in a solvent and removing the
solvent. Suitable polymeric coating materials, include, but are not
limited to polytetraflouroethylene, silicone rubbers, or
polyurethanes, all of which are known to be biocompatible.
Non-polymeric material may alternatively be used.
In another aspect, the invention is directed to a delivery system
for inserting stents into a body of a patient. In general, the
delivery system includes a retractable sheath, a shaft partially
disposed within the sheath and a rotatable locking element disposed
over the sheath.
According to one embodiment, the retractable sheath has a wall of a
flexible material and proximal and distal portions. As used herein,
"distal" refers to an area or direction away from the medical
operator inserting the device, while "proximal" refers to an area
or direction close to the medical operator inserting the device
into the patient. The retractable sheath defines an internal lumen
that extends from the proximal to the distal portion. The internal
lumen holds the stent in its collapsed state at the distal portion
of the sheath. The sheath also defines a first groove and a
longitudinal opening through the wall of the proximal portion. The
first groove and longitudinal opening are connected and lie
perpendicular to one another, forming an "L" or "T" shape.
Optional features of the sheath include a retraction handle,
radiopaque locator bands, and a rounded distal end with a series of
small longitudinal slits. The retraction handle may be disposed on
the proximal portion of the sheath, and provides a grip to pull on
to retract the sheath after insertion into a body of a patient. The
radiopaque locator bands may be disposed on the wall of the sheath,
and assist medical practitioners in positioning the stent under
visualization by X-ray. The rounded distal end facilitates
insertion of the stent in the urinary tract. The slits in the
rounded distal end facilitate retraction of the sheath after
insertion of the delivery system.
According to one embodiment, the shaft is coaxially disposed within
the sheath and slidably movable within the lumen of the sheath. The
shaft comprises at least one second groove. The shaft may further
comprise an insertion handle, which provides a surface to push on
to insert the delivery system into a body of a patient.
In a further embodiment, the rotatable locking element includes a
tongue adapted to engage the first groove of the sheath and the at
least one second groove of the shaft. The locking element is
disposed over the proximal portion of the sheath.
When the tongue engages the first groove of the sheath and the at
least one second groove of the shaft, relative movement between the
sheath and the shaft cannot occur, thereby preventing premature
deployment of the stent. To disengage the sheath from the shaft,
the locking element is rotated, positioning the tongue in the
longitudinal opening of the sheath. This allows relative movement
between the shaft and the sheath, and thus allows retraction of the
sheath over the shaft to deploy the stent. To disengage the tongue
from the at least one second groove of the shaft, a thumb tab may
be disposed on the locking element. Downward pressure on the thumb
tab lifts the tongue out of the at least one second groove of the
shaft. Releasing the tongue from the at least one second groove of
the shaft allows the locking element to slide over the sheath.
The delivery system may include a slidable stop cup disposed on the
sheath. The slidable stop cup is used to position the delivery
system against the head of the penis of a male patient during
insertion of the delivery system into the male urethra. Optionally,
the slidable stop cup may be integrated with the locking element to
stabilize or secure the positioning of the delivery system and the
stent in the urinary tract.
In other aspects, the invention involves methods of placing stents,
such as those previously described. One method of placing these and
other collapsible and expandable stents into a body of a patient
comprises collapsing the stent, inserting it into the distal
portion of the sheath of the delivery system of the invention,
inserting the delivery system into the body of the patient,
retracting the sheath over the shaft, and removing the delivery
system from the body of the patient, thereby deploying the stent
within the body. An alternate method of placing the domed stent of
the invention comprises providing the domed stent, positioning a
conventional guidewire stylet assembly within the domed stent,
inserting the guidewire stylet assembly into a body of a patient,
and removing the assembly from the body of the patient, thereby
deploying the domed stent within the body.
In another aspect, the invention involves methods for removing
stents of the invention from a body of a patient after they have
served their purpose. Removal of the stents of the invention
comprises providing a cystoscope and a grasping device, inserting
the cystoscope and grasping device into the body of the patient,
locating the stent with the cytoscope, attaching the grasping
device to the wall of the stent, removing the grasping device
attached to the stent from the body, and removing the cystoscope
from the body.
In yet another aspect, the invention involves methods of making the
stents and delivery systems of the present invention. A method of
making stents of the invention comprises injection molding the
stent as one continuous piece. Alternatively, a method of making
the domed stent comprises injection molding the body segment and
proximal end segment in one mold, separately injection molding the
dome in a second mold, and securing the individual components to
one another. Similarly, a method of making the delivery systems of
the invention comprises extruding the sheath, injection molding the
other individual components and securing them together.
The foregoing and other objects, aspects, features, and advantages
of the invention will become more apparent from the following
description, the drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, like reference characters generally refer to the
same parts throughout the different views. Also, the drawings are
not necessarily to scale, emphasis instead generally being placed
upon illustrating the principles of the invention.
FIG. 1 is a perspective view of one embodiment of the stent of the
invention with a double funnel configuration.
FIG. 2 is a longitudinal cross-sectional perspective view of the
stent of FIG. 1.
FIG. 3 is an enlarged longitudinal cross-sectional front view of
the distal end segment of the stent of FIG. 1 with a portion of the
elastic member shown in phantom line.
FIG. 4 is a cross-sectional view of the lower portion of the male
abdomen illustrating a portion of the urinary tract with the stent
of FIG. 1 positioned in the prostatic urethra.
FIG. 5 is a side view of an alternate embodiment of the stent of
the invention with a domed structure.
FIG. 6 is a top view of the embodiment of the stent of FIG. 5.
FIG. 7 is an expanded longitudinal cross-sectional view of the
domed structure of the stent of FIG. 5.
FIGS. 8A-8B are front views of stents according to the invention in
two alternate collapsed states.
FIG. 9 is a longitudinal cross-sectional view of one embodiment of
the delivery system according to the invention.
FIG. 10 is a side view of the delivery system of FIG. 9.
FIG. 11 is a partial longitudinal cross-sectional view of the
slidable stop cup and the locking element engaging a portion of the
sheath and a portion of the shaft of the delivery system.
FIG. 12 is a transversal cross-sectional view of the locking
element taken along line A--A of FIG. 11, with the insertion and
retraction handles in the background.
FIGS. 13A-13C show a front view (13A), a side view (13B), and a
cross-sectional view (13C) of the locking element of the delivery
system.
FIG. 14 is a partial side view of the delivery system showing the
retractable sheath and the locking element of FIG. 9 and with the
stent partially deployed.
FIGS. 15A-15D illustrate a method for placing a
collapsible/expandable stent into the prostatic urethra of a male
patient using the delivery system of FIG. 9.
FIG. 16 is a side view of a cystoscope and grasping device
extending through a sheath with a locking bridge attached to the
sheath and a telescope in phantom line.
FIG. 16A is a blown-up view in perspective of the tip of the
grasping device.
DESCRIPTION
Stents, according to an illustrative embodiment of the invention,
are useful for maintaining the patency of the prostatic urethra.
Because the size and shape of this body lumen often varies from
patient to patient, the stent is preferably sufficiently flexible
to accommodate anatomical differences, while at the same time,
sufficiently strong to maintain the prostatic urethra open in
response to constrictive forces. Thus, according to the
illustrative embodiment, stents of the present invention are
therefore generally constructed of flexible biocompatible
materials, including, but not limited to silicone, TEFLON.RTM. and
other PTFE polymers, polyurethane polymers, thermal plastics or
malleable metals. Such materials combine the rigidity necessary for
maintaining the prostatic urethra open and able to pass fluids
while also being soft enough for patient comfort. The flexible
material of the stent may be doped with a radiopaque material to
permit visualization by X-ray. Barium sulfate is one example of a
suitable radiopaque agent that may be used with stents of the
present invention.
According to a further feature, the stent of the illustrative
embodiment is collapsible and expandable, and designed for use in
the prostatic urethra of a male patient. Insertion of these and
other collapsible and expandable stents into the patient may be
accomplished by use of delivery systems according to the present
invention, which comprise a retractable sheath, a shaft and a
rotatable locking element.
FIG. 1 depicts one illustrative embodiment of a stent 10. The stent
10 has a body segment 12 including a wall 14 made of a flexible
material and extending between a first terminal end 20 and a second
terminal end 24. The wall 14 has an internal surface 16 and an
external surface 18. In the illustrative stent 10, the first
terminal end 20 is wider than (e.g., has at least one external
diameter greater than) at least some portion of the body segment 12
located between the first 20 and second 24 terminal ends.
In one illustrative embodiment, the first terminal end 20 includes
a first retention ring 22 extending axially from the body segment
12. According to one feature, the first retention ring 22 anchors
the stent 10 at the bladder end of the prostatic urethra, above the
prostate, after insertion into a patient. In the illustrative stent
10, the second terminal end 24 is wider than (e.g. has at least one
external diameter greater than) at least some portion of the body
segment 12 extending between the first and second terminal ends, 20
and 24, respectively. Illustratively, the second terminal end 24
includes a second retention ring 26 extending axially from the body
segment 12. According to one feature, the second retention ring 26
anchors the stent 10 at the external sphincter end of the prostatic
urethra, below the prostate, after insertion into a patient.
Additionally, the stent 10 may employ zero, one or two retention
rings, such as the retention rings 22 and 26.
As skilled practitioners will appreciate, in other embodiments,
only one of the terminal ends 20 and 24 may have an external
diameter, such as diameter 3 or 7, that is greater than the
external diameter, such as the diameter 5, of an intermediate
portion of the body segment 12. In the illustrative stent 10, both
the external cross-sectional diameters 3 and 7 of the terminal ends
20 and 24, respectively, are greater than the external
cross-sections diameter 5 of an intermediate portion of location
along the wall 14, between the first and second terminal ends 20
and 24. This configuration creates a funnel or hourglass shape to
facilitate maintaining the stent 10 in position within the
prostatic urethra. For example, in one illustrative embodiment, the
diameter 5 of the body segment 12 is between about 18 French and
about 21 French, while the diameters 3 and 7 of the first and
second terminal ends 20 and 24, respectively, are between about 22
French and about 26 French. By varying the diameters 3, 5 and 7 and
the length of the body segment 12, the stent 10 may be tailored to
the individual needs of particular patients.
According to the illustrative embodiment, the stent 10 may also be
designed according to the individual needs of particular patients
in other ways. For example, the total length of the stent 10 may be
varied between about 1.0 inch and about 2.5 inches, to accommodate
the size of a patient's prostatic urethra, which varies in length
from about 0.6 inches to about 3.0 inches. To determine the length
of the patient's prostatic urethra, a conventional measuring
catheter may be employed.
According to a further illustrative feature the diameters 3, 5
and/or 7 may be varied in size, relative to each other, to cause
the wall 14 of the body segment 12 to be sloped at various angles.
By way of example, for patients with wide prostatic urethras, the
ratio of, for example, diameter 3 to diameter 5 may be made
sufficiently large to cause the wall 14 to slope slopes sharply in
an outward direction to ensure that the double funnel configuration
anchors in place within the patient's body. The ratio between the
diameter 7 and the diameter 5 may be similarly configured. In a
further embodiment, for patients with narrower internal
physiologies, the ratio of diameter 3 to diameter 5 and/or diameter
7 to diameter 5 may be selected to be small enough to avoid the
potential discomfort associated with an ill-fitting stent, but
large enough to anchor the stent 10 within the patient's body.
To provide drainage of fluid from a patient's bladder, a lumen 28
may extend through the body segment 12 between the first terminal
end 20 and the second terminal end 24. Alternatively or
additionally, drainage may be provided or enhanced by grooves
located on the external surface 18 of the wall 14. Optionally, the
wall 14 of the body segment 12 may define one or more through-holes
30 disposed along its length. Through-holes may also be disposed in
the first and second terminal ends 20 and 24, respectively, or in
the first and second retention rings 22 and 26, respectively.
The through-holes 30 extend through the external surface 18 to the
internal surface 16 of the stent 10, and provide for fluid
communication with the lumen 28 to facilitate urinary drainage. As
illustrated in FIG. 2, the various through-holes 30 define openings
through the wall 14 of the stent 10, shown in cross section. To
avoid tissue in-growth and to maximize drainage, the diameter of
the through-holes 30 in the disclosed embodiments is preferably
between about 0.06 in. to about 0.12 in.
The thickness t and hardness h of the stent 10 affect its
collapsible and expandable properties. If the stent 10 is too thick
and/or too hard, the body segment 12 will not collapse to permit
insertion into a patient's body. If the stent 10 is too thin and/or
too soft, it may tear during or after insertion into a patient's
body leading to potential medical complications. It may also fail
to provide adequate support to the prostatic urethra. The thickness
t, as shown in FIG. 2, is illustratively between about 0.01 in. and
about 0.08 in. The hardness h is illustratively between about 35
shore A and about 65 shore A, with 50 shore A preferred.
FIG. 3 shows a cross-sectional view of the first retention ring 22
extending axially from the first terminal end 22. In one
embodiment, the first retention ring 22 is fabricated from the same
flexible material as the body segment 12. As shown in FIG. 3, the
illustrative first retention ring 22 includes an annular elastic
member 32 to reinforce the first retention ring 22. The elastic
member 32 may be embedded within the flexible material of the
retention ring 22 or bound to a surface or groove of the first
retention ring 22. Illustratively, FIG. 3 shows the elastic member
32 embedded within the first retention ring 22. According to the
embodiment of FIG. 3, the elastic member 32 circumscribes the first
retention ring 22.
The elastic member 32 may also be fabricated from a material having
"superelastic" properties. Such a material may include alloys of
In--Ti, Fe--Mn, Ni--Ti, Ag--Cd, Au--Cd, Au--Cu, Cu--Al--Ni,
Cu--Au--Zn, Cu--Zn, Cu--Zn--Al, Cu--Zn--Sn, Cu--Zn--Xe, Fe.sub.3
Be, Fe.sub.3 Pt, Ni--Ti--V, Fe--Ni--Ti--Co, and Cu--Sn. In the
illustrative embodiment, the superelastic material includes a
nickel and titanium alloy, known commonly as Nitinol.RTM. available
from Memry Corp of Brookfield, Conn. or SMA Inc. of San Jose,
Calif. The ratio of nickel and titanium in Nitinol.RTM. can vary.
One preferred example includes a ratio of about 50% to about 56%
nickel by weight. Nitinol.RTM. also possesses shape retention
properties.
FIG. 4 is a conceptual diagram depicting an illustrative placement
of the stent 10 within a prostatic urethra 38 of a male patient. As
seen in FIG. 4, the first terminal end 20 of the stent 10 rests
above the prostate, at the bladder end of the prostatic urethra 38,
while the second terminal end 24 of the stent 10 lies below the
prostate, above the external sphincter 42. According to the
illustrative embodiment, no part of the stent 10 extends through
the external sphincter 42. Such positioning relative to the
external sphincter 42 is preferable to avoid.
The details of the internal anatomy shown in FIG. 4 include the
prostate gland 34, the urethra 36 (spanning from the penile urethra
37 through the bulbous urethra 39 and to the prostatic urethra 38),
the bladder 40 and the external sphincter 42. The urethra 36 is the
channel that conducts urine from the bladder 40 to the penis 44 for
discharge from the body. The inside diameter of the urethra 36 is
variable and may typically extend to about 0.8 in. The prostatic
urethra 38 is a segment of the urethra 36 that tunnels through the
prostate gland 34 and joins the prostate gland 34 to the urethra
36. Urine flows from the bladder through the prostatic urethra 36
to the bulbous urethra 39 and to the penile urethra 37 out of the
body. The external sphincter 42 controls the flow of urine from the
bladder 40.
FIG. 5 depicts a stent 46 according to another illustrative
embodiment of the invention. The stent 46 has a body segment 48.
The body segment 48 is formed from a wall 50 of flexible material
extending between a first terminal end 54 and a second terminal end
62. As shown in FIG. 5, the first terminal end 54 has external
cross-sectional diameter 39. Similarly, the second terminal end 62
has an external cross-sectional diameter 43. The stent 46 also has
at least one intermediate external cross-sectional diameter 41.
According to the illustrative embodiment, both external diameters
39 and 43 are larger than the intermediate external diameter 41 to
facilitate anchoring the stent 46 in place within the body of a
patient. According to a further embodiment, a portion 53 of the
body segment 48 located adjacent to the first terminal end 54
tapers to increase the cross-sectional diameter 39 of the first
terminal end 54. Similarly, a portion 66 of the body segment 48
located adjacent to the second terminal end 62 flares to increase
the cross-sectional external diameter 55 of the second terminal end
62. To further anchor the stent 46 in place within a patient's
body, the second terminal end 62 includes a retention ring 64
extending axially from the body segment 48. Illustratively, the
wall 50 has an external surface 52 and an internal surface (not
shown) defining a lumen 51.
According to the illustrative embodiment of FIG. 5, the collapsible
and expandable nature of the stent 46 is enhanced by annular
collars 68, varying of the wall thicknesses t and providing at
least one slot 70 disposed along the body segment 48. The annular
collars 68 lie along various sections of the body segment 48 and
serve as breaking points to radially collapse the stent 46. The
wall thickness t of the body segment 48 decreases towards the
annular collars 64. In one illustrative embodiment, the portion of
the wall 50 that lies near the annular collars 64 has a t value of
about 0.010 inches to about 0.30 inches with about 0.20 inches
preferred. As the wall 50 extends away from the annular collars,
the t value increases to between about 0.035 inches to about 0.055
inches, with about 0.04 in. preferred.
In one illustrative embodiment, the slots 70 are formed as concave
inner or outer surfaces in the wall 50 of the body segment 48. In
an alternative embodiment, the slots 70 are formed as through
openings in the wall 50. In FIG. 5, the slots 70 are formed as
through openings in the wall 50. These slots 70 enhance the
collapsible properties of the stent 46. In addition, where the
slots 70 are formed as concave surfaces, the surface area of the
stent 46 is increased, allowing swollen prostate tissue to occupy
these surfaces to further anchor the stent 46 in position within a
body of a patient, without favoring encrustation of the stent 46.
The size of the slots 70 is not confined to predetermined
dimensions, but may vary, provided collapsibility is enhanced and
the stent 46 retains an expandable structure. Optionally, a suture
55 may loop through a slot 70 defining an opening at the end
segment 62 to facilitate removal of the stent 46.
According to a further feature, the first terminal end 54 includes
a hollow dome 56 extending axially from the body segment 48.
Rounded shoulders at the top of the dome 56 facilitate insertion of
the stent 46 into small openings, such as the male urethra 36. The
dome 56 includes at least one through-hole 58 adapted for urine
transfer into the lumen 51.
The lumen 51 extends through the body segment 48 from the first 62
to the second end 54 to provide fluid communication between the at
least one through-hole 58 and the urethra. Bodily fluid from the
bladder drains into the at least one through-hole 58 residing in
the dome 56 and into the body segment 48 to be released through the
first terminal end 62 into the urethra.
The dome 56, with its through-hole configuration, acts as a filter,
allowing fluids and small harmless solid materials, such as blood
clots, to pass, while preventing large blood clots and other solid
materials, such as calculi or stone debris, from occluding the
lumen and interrupting the passage of fluids through the stent 46.
In one embodiment, the through-holes 58 have a diameter between
about 0.06 inches and about 0.1 inches, with about 0.09 inches
preferred. In one illustrative embodiment, the dome 56 includes two
to six through-holes 58. In one particular embodiment, the dome 56
includes four through-holes. The through-holes may be disposed at
various intervals (regular or irregular) along the surface of the
dome. For example, FIG. 6 shows four through-holes 58 disposed at
four different locations along the dome 56. In the illustrative
embodiment of FIG. 6, the centers of the four through-holes 58 lie
at 0.degree., 90.degree., 180.degree., and 270.degree. angles along
the periphery of the dome 56. The through-holes 58 may, however,
lie at any combination of angles along the periphery of the dome
56.
As shown in FIGS. 5 and 6, the dome 56 may terminate in a
protuberance 60, which facilitates insertion of the stent 46. The
protuberance 60 is useful, for example, when the stent is inserted
with a conventional guidewire stylet assembly, known to those of
skill in the art. As seen in FIG. 7, the protuberance 60 may define
a small lumen 61 for insertion of a guidewire through the stent 46.
The lumen 61 of the protuberance 60 is preferably between about
0.039 inches and about 0.049 inches in diameter to accommodate
conventional guidewires.
According to the illustrative embodiment of the invention, after
the stents 10 and 46 have been collapsed, delivery systems of the
invention may be used to introduce these and other
collapsible/expandable stents into a body of a patient. FIGS. 8A-8B
depict the domed stent 46 in its collapsed state in two possible
configurations. In FIG. 8A, the wall 50 of the body segment 48 of
the stent 46 is collapsed along the slots 70. In FIG. 8B, the stent
46 is folded in half on itself along line B--B.
FIG. 9 shows one embodiment of a delivery system 80 used to
introduce these and other collapsible and expandable stents into a
body of a patient. In general, the delivery system 80 comprises a
retractable sheath 82, a shaft 84, and a rotatable locking element
86.
The retractable sheath 82 has a proximal portion 88 and a distal
portion 90. The sheath 82 defines an internal lumen that extends
from the proximal portion 88 to the distal portion 90 for housing a
portion of the shaft 84 and holding the stent 10. The sheath 82
further defines a first groove 81 transversal to the length of the
sheath 82.
The retractable sheath 82 is made of a wall 85 of flexible
material. Preferred flexible materials include, a high density
polyethylene or a polypropylene based extrusion. According to the
illustrative embodiment, the thickness of the wall 85 of the
retractable sheath 82 is between about 0.050 inches and about 0.060
inches. According to one embodiment, the thickness of the wall 85
is about 0.055 inches. In one embodiment, the inner diameter of the
sheath 82 is between about 0.280 inches and about 0.340 inches.
According to one embodiment, the inner diameter of the sheath 82 is
about 0.312 inches. According to a further embodiment the inner
diameter of the sheath 82 is sized to accommodate the stent 10 in
its collapsed state.
A retraction handle 97 may be disposed on the proximal portion 88
of the sheath 82. The retraction handle 97 is adapted to proximally
retract the sheath 82. The retraction handle 97 may include two
finger grips 99 and 101, which allow medical practitioners to more
easily retract the sheath 82 by pulling back on the finger grips 99
and 101.
The shaft 84 includes a proximal end 98 and a distal end 100, and
further includes at least one second groove 83. The at least one
second groove 83 may be a notch limited to the top surface of the
shaft 84, in which case the shaft 84 is rotatable with the locking
element 86. Alternatively or additionally, the at least one second
groove 83 may be a carved-out section of the shaft 84 that wraps
circumferentially around the shaft 84 along a 90.degree.,
180.degree., 270.degree., or 360.degree. path, in which case the
shaft 84 need not be rotatable.
The shaft 84 is preferably about 10 in. in length, and is
preferably at least twice as long as the stent 10 being deployed.
Thus, the length of the shaft 84 varies depending on the length of
the stent 10 and the patient's internal anatomy. The distal end 100
of the shaft 84 may expand radially to form a plunger shape that
abuts the stent 10.
An insertion handle 102 may be disposed on the proximal end 98 of
the shaft 84. The insertion handle 102 is adapted to insert the
delivery system 80 into the body of a patient. FIG. 10 is a top
view of the insertion handle 102 with the retraction handle 97
lying behind it in the background.
The rotatable locking element 86 is disposed over the proximal
portion 88 of the sheath, and comprises a tongue 114. The tongue
114 is adapted to engage the first groove 81 of the sheath 82 and
the at least one second groove 83 of the shaft 84. Referring to
FIG. 11, the illustrative locking element 86 includes a proximal
end 106, a distal end 108, a top portion 110 and a bottom portion
112. In FIG. 11, the tongue 114 is disposed on the distal end 108
under the top portion 110 of the locking element 86, but may be
positioned elsewhere on the locking element 86 provided it can
engage both the first groove 81 of the sheath 82 and the at least
one second groove 83 of the shaft 84. When the delivery system is
in the locked position, the tongue 114 engages the first groove 81
of the sheath 82 and the at least one second groove 83 of the shaft
84. A more detailed view of the locking element 86 and its mode of
operation is shown in FIGS. 12 and 13A-13C.
FIG. 12 is a cross-sectional view of the distal end 108 of the
locking element 86 taken along line A--A of FIG. 11. In FIG. 12,
the tongue 114 is engaging the first groove 81 of the sheath 82 and
the at least one second groove 83 of the shaft 84. This
configuration prevents relative movement between the sheath 83 and
the shaft 84 during insertion of the delivery system into a body of
a patient. FIG. 12 also shows the insertion handle 102 and the
retraction handle 97 in the background.
FIG. 13A is a front view of one embodiment of the locking element
86. In this embodiment, opposing "S" shaped slits 150 in the top
surface of the locking element 86 define the thumb tab 116. The top
surface of the locking element 86 further defines two longitudinal
slits 152 that lie on either side of the tongue 106. A pivot point
154 sits between the "S" shaped slits 150 and the longitudinal
slits 150, allowing a medical practitioner to lift the tongue 106
by depressing the thumb tab 116.
The locking element 86 may be reinforced with a series of ribs 156,
which comprise areas of increased internal wall thickness. In FIG.
13A, the ribs 156 are shown in phantom. The ribs 156 provide added
circumferential strength to the locking element 86 during rotation
and engagement of the tongue 106.
FIG. 13B is a side view of the locking element of FIG. 13A taken
along line B--B. As shown more clearly in FIG. 13B, the ribs 156
comprise raised internal surfaces of the interior of the locking
element 86. One of the ribs 156 reinforces the thumb tab and
extends to the tongue 114.
FIG. 13C is a cross-sectional view of FIG. 13A, taken along line
C--C. In FIG. 13C, the ribs 156 lie at regular intervals in a
quadrant configuration. The ribs 156 need not, however, lie at
regular intervals or in any particular configuration, emphasis
instead being placed on sufficient reinforcement for the locking
element 86. FIG. 13C also shows the tongue 114 and the longitudinal
slits 150. The central hole 158 that surrounds the tongue 114 of
FIG. 13C allows the locking element 86 to slide over the shaft 84
after the tongue 114 is disengaged from the sheath 82 and shaft
84.
After insertion of the delivery system into the body of the
patient, the sheath 82 is withdrawn over the shaft 84 to deploy the
stent 10. Referring to FIG. 14, a more detailed view of the
structure of the retractable sheath 82 is provided. The retractable
sheath 82 defines an internal lumen 89, which extends from the
proximal portion 88 to the distal portion 90 and contains the stent
10 within the distal portion 90.
The retractable sheath 82 further defines the first groove 81 and a
longitudinal opening 94 through the wall 85 of the proximal portion
88 of the sheath 82. The longitudinal opening 94 comprises a
proximal end 96 and a distal end 93. The proximal end 96 of the
longitudinal opening 94 is connected to and lies perpendicular to
the first groove 81, forming an "L" or "T" shape. A portion of the
shaft 84 may be seen through the distal end 93 and proximal end 96
of the longitudinal opening 94 of the sheath 82.
To disengage the tongue 114 from the first groove 81 of the sheath
82, the locking element 86 is rotated one-quarter turn clockwise to
position the tongue 114 within the longitudinal opening 94 of the
sheath 82, allowing relative movement between the sheath 82 and the
shaft 84. FIG. 14 depicts the tongue 114 positioned within the
longitudinal opening of the sheath 82. When the at least one second
groove 83 is limited to a notch on the top surface of the shaft 84,
rotation of the locking element 86, rotates the shaft 84 to
maintain the tongue 114 within the at least one second groove 83 of
the shaft 84. When the at least one second groove 83 of the shaft
84 wraps circumferentially around the shaft 84, rotation of the
locking element 94 need not rotate the shaft 84 to maintain the
tongue 114 within the at least one second groove 83, as the tongue
114 is merely re-positioned around the circumferential length of
the same at least one second groove 83 of the shaft 84.
To facilitate insertion and withdrawal of the sheath 82 in and from
the patient, the distal portion 90 of the sheath 82 may terminate
in a rounded autramatic tip, which may comprise any number of slits
91 from two to six slits with four slits typical. The slits come
together at the end of the rounded tip in a star-like
configuration. The slits 91 facilitate proximal retraction of the
sheath 82 by opening widely over the stent 10 during retraction
over the shaft 84.
At least one radiopaque locator band 95 may be disposed on the wall
85 of the sheath 82. For example, two radiopaque locator bands 95
may be used to mark the stent 10 contained within the sheath 82
(such as shown in FIGS. 15A-D). Radiopaque locator bands 95 guide
the medical practitioner (e.g. the physician) in positioning the
stent 10 within a body of a patient under visualization by X-ray.
The radiopaque locator bands 95 may be comprised of heavy metals,
such as steel, tantulum, gold rings or the like.
In an alternate embodiment, a thumb tab 116 may be disposed between
the proximal and distal ends 106 and 108 of the top portion 110 of
the locking element 86 as shown in FIG. 11. The thumb tab 116 may
be effaced within the profile of the locking element 86, or it may
rise radially and outwardly at an angle with the tongue 114 to
provide for greater pivoting angles to the tongue 114. Referring to
FIG. 11, the tongue 114 of this embodiment is retractable from the
grooves 83 of the shaft 84, and the locking element 86 is slidable
along the length of the shaft 84. Downward pressure on the thumb
tab 116 raises the tongue 114 out of the at least one second groove
83 of the shaft 84. This embodiment further comprises a slidable
stop cup 104 disposed distal to the locking element 86 on the shaft
84. In addition, the grooves 83 comprise about 40-50 grooves spaced
at approximately 10 grooves per in., spanning approximately half of
the length of the shaft 84 at its distal end 100.
The locking element 86 may be used to distally advance the slidable
stop cup 104 along the length of the shaft 84. After disengaging
the tongue 114 from the first groove of the sheath 82 by rotating
the locking element 86 to position the tongue 114 in the
longitudinal opening 94, and disengaging the tongue 114 from the at
least one second groove 83 by depressing the thumb tab 110, the
locking element 86 becomes slidable along the length of the shaft
84.
The slidable stop cup 104 is used to position and stabilize the
delivery system 80 against a body of a patient before deploying the
stent 10. For example, after inserting the delivery system 80 into
the prostatic urethra 38, the medical practitioner rotates the
locking element 86, depresses the thumb tab 116, and slides the
locking element 86 along the shaft 84 to advance the stop cup 104
along the shaft 84 until the stop cup 104 lies against the meatus
in the head of the penis. At this point, the thumb tab 116 is
released, re-engaging the tongue of the locking element 86 into one
of the plurality of second grooves 83 of the shaft 84, thereby
locking the slidable stop cup 104 in place. The tongue 106 does
not, however, re-engage the first groove 81 of the sheath 82, but
rather remains in the longitudinal opening 94 of the sheath 82 to
allow relative movement between the sheath 82 and the shaft 84.
FIGS. 15A-15D illustrate a method of inserting a stent of the
invention into the body of a patient with a delivery system of the
invention. To load the stent 10 into the delivery system 80, manual
or automated pressure is exerted on the body segment 12 and the
proximal and distal end segments 20 and 24 of the stent 10 to
collapse it (as in FIGS. 8A-B), and the collapsed stent 10 is
placed within the sheath 82 through an opening in its proximal
portion 88 or its distal portion 90. The collapsed stent 10, may be
so placed by the manufacturer prior to sale, or by the medical
practitioner prior to insertion.
With the stent 10 in place, the delivery system 80, in its locked
configuration, is introduced into the body of a male patient
through the meatus 117 in the head 118 of the penis 120 into the
urethra 36 as shown in FIG. 15A. In doing so, a medical
practitioner may hold the head 118 of the penis 120 in one hand and
exert pressure in a distal direction on the insertion handle 102
with the other hand. Under X-ray vision, the medical practitioner
may use the radiopaque locator bands 95 to help position the
delivery system 80 through the urethra, so that the distal portion
90 of the sheath 82, containing the two radiopaque locator bands
95, is located within the prostatic urethra 38 surrounded by the
prostate gland 34 and above the external sphincter 42.
During insertion, the delivery system 80 is in its locked
configuration to prevent premature deployment of the stent 10. The
tongue 114 of the locking element 86 engages the first groove 81 of
the sheath 82 and one of the plurality of grooves 83 of the shaft
84 to prevent relative movement between the sheath 82 and the shaft
84 (FIG. 11).
The locking element 86 may also be used to advance the slidable
stop cup 104 against the head 118 of the penis 120. To position the
slidable stop cup 104, the locking element 86 is rotated
one-quarter turn clockwise to disengage the tongue 106 from the
first groove 81 of the sheath 82, thereby positioning the tongue
106 in the longitudinal opening 94 of the sheath 82 (FIG. 14). The
thumb tab 116 is then depressed, disengaging the tongue 106 from
one of the plurality of grooves 83 of the shaft 84, so that the
locking element 86 becomes slidably movable along the length of the
shaft 84. This allows the medical practitioner to use the locking
element 86 to distally advance the slidable stop cup 104 to the
head 118 of the penis 120.
Referring to FIG. 15B, the locking element 86 has been advanced
distally along the length of the delivery system 80 exposing the
first groove 81 of the sheath 82, and positioning the slidable stop
cup 104 at the head 118 of the penis 120. Once the slidable stop
cup 104 is in this position, the thumb tab 116 is released,
re-engaging the tongue 106 into another of the plurality of grooves
83 of the shaft 84, preventing movement of the slidable stop cup
104 backwards. The locking element 86 thereby maintains the
slidable stop cup 104 against the head 118 of the penis 120, and
secures the distal end 90 of the delivery system 80 within the
prostatic urethra 38.
As FIG. 15C illustrates, after the slidable stop cup 104 is
positioned against the head 118 of the penis 120, the sheath 82 is
withdrawn, exposing and releasing the stent 10. To withdraw the
sheath 82, the locking element 86 is rotated to position the tongue
106 within the longitudinal opening 94 of the sheath 82, allowing
relative movement between the sheath 82 and the shaft 84. The
medical practitioner then proximally withdraws the retraction
handle 97 by positioning some fingers on the finger grips 99 and
101 and exerting pressure in a proximal direction. As the
retraction handle 97 is slowly retracted, the sheath 82 moves
backward, thereby partially deploying the stent 10 within the
prostatic urethra 38 of the patient, as shown in FIG. 15C.
To fully deploy the stent 10 within the prostatic urethra 38, the
sheath 82 is completely withdrawn over the stent 10 by the
retraction handle 97, and the delivery system 80 is then removed
from the body. Under these circumstances, the stent 10 reverts to
its expanded geometry. FIG. 15D shows the expanded stent 10
deployed within the prostatic urethra 38 of the male patient, once
released from the delivery system.
Once the stent has served its purpose, it is removed to avoid
infection. Removal of the stent may be accomplished through use of
a cystoscope and a conventional grasping device, shown in FIG. 16.
FIG. 16 shows a grasping device 122 with forward forceps 124
disposed within a sheath 126 secured to a bridge 128 adapted to
receive a cystoscope 127. A detail of the forward forceps 124 is
illustrated in FIG. 16A.
In addition to the forward forceps 124, the grasping device 122
further comprises an axially elongated shaft 130 and scissors-like
handles 132 disposed co-planar and at an angle with the elongated
shaft 130 at a proximal portion 134 of the assembly. The
scissors-like handles 132 are used to manipulate the forward
forceps 124. The diameter of the sheath 126 must be large enough to
accommodate the elongated shaft 130. The cytoscope 127 comprises a
telescopic lens 136 for viewing a body lumen, and a port 138 for
irrigating or draining the body lumen.
To remove stents of the invention from a body of a patient with the
cytoscope grasping device assembly, a medical operator inserts the
assembly into the urethra of the patient, locates the stent
disposed within the prostatic urethra through the telescopic lens
136, manipulates the scissors-like mechanism 132 to close the
forward forceps 124 on a wall of the stent, pulls the grasping
device 122 proximally to remove the stent from the body of the
patient, and removes the cystoscope 127 from the body.
Alternatively, removal of the stents of the invention may occur by
proximally withdrawing the thread of suture material 55 (FIG. 5)
until the stent 46 is pulled through the meatus of the head of a
penis. As shown in FIG. 15D, the thread of suture material 55 is
looped and threaded through an opening in the wall of the stent 10,
and extends through the urethra to the exterior of the body where
it can be easily grasped.
One illustrative method of manufacturing stents according to the
illustrative embodiment of the invention (FIGS. 1 and 5) includes
injection molding each stent of the invention as a single
continuous piece or separately injection molding the various
components, such as the dome and the body segment and securing
these individual components together by suitable means, including
but not limited to solder, weldment, or adhesive.
Injection molding includes providing an injection mold that
profiles the different structural features of the stents, injecting
liquid silicone or thermal plastic into the mold, allowing the mold
to cure, and removing the cured structure from the injection mold.
To provide an internal lumen, a core pin may be positioned down the
center of the injection mold. The injection mold may further
include protrusions extending from the inner surfaces of the mold
for incorporating through-holes or slots into the stent.
Alternatively, these features may be added to the stent after it is
cured. To reinforce the stents with an elastic member, such as
nitinol, the mold may incorporate the elastic member in the
appropriate position, or the elastic member may be introduced
through a small axial lumen incorporated into the mold after the
stent is cured, or the elastic member may be taped or glued to the
stent.
According to one embodiment, method of making the delivery system
of the invention includes extruding the sheath, independently
injection molding other individual parts, such as the shaft,
locking element, slidable stop cup and insertion and retraction
handles, and securing these individual parts together by suitable
means, including but not limited to solder, weldment, or adhesive
to assemble the delivery system.
Variations, modifications, and other implementations of what is
described herein will occur to those of ordinary skill in the art
without departing from the spirit and scope of the invention.
Accordingly, the invention is to be defined not only by the
preceding illustrative description.
* * * * *